Selected lesions placed unilaterally in specific brain sites will be evaluated for their effect upon phonation in monkeys. Evidence for lateralization of phonatory control will be sought by testing performance in a discriminative phonation task and by study of spontaneous phonatory behavior in the home colony environment. Evaluation of general apraxia will be made by analyzing concurrent performance of a non-vocal bar-pressing behavior. Sequential damage to bilaterally-symmetrical structures will reveal whether inter-hemispheric interactions are in effect for the regulation of primate phonation. Assessment of effects of damage to cortical regions with input to anterior cingulate cortex (i.e., neocortical areas 7,9,10,22) and those with input from anterior cingulate cortex (dorsal hypothalamus, amygdala) will provide data that will help resolve the interaction issue. Data from these studies will help to achieve better understanding of neuropathologies affecting vocal function.